About Stair Calculations
Designing a safe and comfortable staircase requires careful calculation of several key dimensions. Our stair calculator helps you determine the optimal number of steps, riser height, and tread depth based on building codes and available space.
Key Stair Design Terms
- Rise: The vertical height of each step
- Run: The horizontal depth of each tread
- Total Rise: The overall vertical height from floor to floor
- Total Run: The horizontal space available for the staircase
- Nosing: The edge of a tread that overhangs the riser
- Stringers: The structural support for the treads and risers
Building Code Standards
Most building codes specify requirements for stairs to ensure safety. Common standards include:
- International Building Code (IBC): Maximum riser height of 7 inches; minimum tread depth of 11 inches
- International Residential Code (IRC): Maximum riser height of 7.75 inches; minimum tread depth of 10 inches
- Riser height and tread depth should be consistent throughout the staircase
- Minimum stair width of 36 inches for residential use
Stair Design Formulas
A common rule of thumb for comfortable stairs is that the sum of two risers and one tread should equal about 24-25 inches. Another useful formula is:
Riser height (in inches) × Tread depth (in inches) = 70-75
This helps create stairs that feel natural to climb and descend.